Salmonella typhimurium tester strains have been used to examine the metabolic activation of chemical carcinogens by rabbit liver and lung cytochromes using mutation as the end point. This project is designed to study the ability of different forms of cytochrome P450 present in lung tissue to activate known carcinogens to mutagenic metabolites. It will also allow a comparison to be made on the relative metabolic activating abilities of lung and liver.